Catalyst recovery in hydrocarbon synthesis processes



Aug. 16, 1949. M.- A. SEGURA 2,479,420

CATALYST RECOVERY IN HYDROCARBON SYNTHESIS PROCESSES Filed Sept. 26,1946 CO4R$E IRON STORAGE JP CONVEYOR V i DRAW OFF DRAIN cvwsrm & [STEAM0i? GA$MILET m! vmwm:

' MAQNELL A. 3.5 am,

UNITED STATES PATENT OFFICE CATALYST RECOVERY IN HYDROCARBON SYNTHESISPROCESSES Marnell A. Segura, Dcnliam Springs, La., assignor to StandardOlI Development Company, a corporation of Delaware Application September26, 1946, Serial No. 699,561

10 Claims. (Cl. 260-4493) 1 My present invention relates to thesynthesis of hydrocarbons from carbon monoxide and hydrogen in thepresence of an iron catalyst and in particular it relates to thehandling of a powdered settler, bottom draw-off fluid catalyst reactorand hydrogen to form hydrocarbons and oxygenated hydrocarbons. In thecase where the catalyst ro yst employ in a fl d C l yp f is powderediron, carbonaceous deposits form on process in such a manner as toinsure good fluidithe catalyst not only impairing its activity, butzation of the catalyst with minimum catalyst worse still causingphysicaldisintegration thereof. losses due to excessive attrition, allof which will That is to say, the catalyst powder contaminated morefully appear hereinafter. with carbonaceous deposits may be procured inIt is known, of course, that in chemical reaca readily fluidizable stateby maintaining it in the lio involving a gas and solid, e ore Stfollowing particle size and distribution: tionary beds of the latterhave been used, the gas being forced through the bed or beds under 3:23is: 3 the proper conditions. The use of fluidized 40430 micgons lessthan powdered catalyst is also a matter of record and 80 0 plus micronsless than 35% commercial practice. In the latter process, the (allmaterial less than 100 mesh) gasiform material is caused to flowupwardly through areaction zone under controlled velocities When, inoperation, there is an increase in the in contact with a powderedcatalyst thus forming amount of catalyst fines, the same is evidenced adense, turbulent, ebullient suspension of the 29 by a large temperaturegradient from the top to powder in the gasiform material. the bottom ofthe fluid bed. That is to say, sup- In many chemical processes employingthe pose the cataiyst bed to be to feet in depth, fluid catalysttechnique, contaminating deposits then under good fluidization of thecatalyst, no form on the catalyst during the process. These two pointsin the bed will have a te p deposits not only impair. the activity ofthe 25 difference exceeding 4 to 5 F. But when this catalyst but in thecase of certain reactions such temperature difference from the top tothe botas the hydrocarbon synthesis reaction, interfere tom of the bedamounts to say 50 F., poor fluidi- With the fluidization of the catalystso that inzaticn is indicated. Another indication of poor stead ofremaining in the reaction zone as a dense fiuidization is the drop inthe heat transfer cotu ulent su p s n it te ds t dis nt at 30 efficientand the development of hot spots in the phys y, and pass o o e reactor t15 9- bed. These conditions usually become severe This is hly un s l f te ol o i enough to necessitate discontinuing the operation sons. Thelatest fluid catalyst reactor designs t change catalyst when t finehaving a partiare of the bottom draw-off type which signifies e16 Sizeof 0 t 0 microns amount to to 5 per that catalyst removed for one reasonor another, 35 cent of the To give more details, it has been Such as Wreheat or 0001, or to regenerate the found that u the fluidized bed ofiron catalyst Same is Withdrawn from W at the side or does not have theproper particle size distribution P e only porno is entrained in theheat transfer coefficient will be poor, which the gaslform mammalpassing from the top of causes poor fiuidization, large losses ofcatalyst the reactor. This type of reactor is of course very so finesfrom the bed, Door heat transfer and large m preferred to the overheaddrawofi type temperature gradients. As to heat transfer the sinceit.greatly.reduces the of gas'sonds following data show the eifect ofimproper particontactmg devices required outside the reactor, cle sizedistribution and the method of curing to separate catalyst from gasesand/or vapors.

But as stated, in the bottom draw-ofi type of reactor, unless theparticle size and distribution Rona Analysis has) A B C of the catalystis maintained within prescribed limits, a proper separation of catalystfrom gasitfio gilfii form material will not occur within the reactor andcopious quantities of catalyst will pass out e t Tmnsfeskiifiiii, B. t.u./(Hr.) (sof of the reactor with the vapors, fumes, gases, etc., 100 4090 thus incurring an expensive and diflicult catalyst separationproblem. v Condition A is that at the start of a run before One aspectof my invention relates, as indiany catalyst disintegration. Condition Bis that cated, to handling powdered catalyst in a delayed after seriousdisintegration, resulting in greatly lowered heat transfer coefllcientto the cooling surface disposed within the bed. Coarse catalyst of80-200 microns is now added to the extent of 60% by weight of thecatalyst already present. This gives condition C, in which the particlesize distribution, and accordingly the coemcient, are restored nearly toA.

In the example given, 60% of 80-200 micron size was added to correct theparticle size distribution. Obviously an analysis must be madeperiodically of the particle sizeof the iron powder in the bed and thenby calculation the proper amount of coarse resintered or fresh powdermay be added so as to form a bed of the proper particle sizedistribution within the limits herein prescribed. As stated, the mainbulk of the catalyst will have a particle size of from 40 to 200microns.

According to my invention, I withdraw catalyst from the reactor,resinter the same and return the resintered material to the reactor, ofa size in which it can be readily fluidized, all of which will morefully appear presently.

In the accompanying drawing, I have shown diagrammatically an apparatusin which a preferred modification of my invention may be carried intoeffect.

Referring in detail to the drawing, i represents a fluid catalysthydrocarbon synthesis reactor. It will not be necessary for a properunderstanding of my invention that the method of carrying out thesynthesis proper be described in detail. It will suflice to say that inreactor i a mixture of carbon monoxide and hydrogen is fed to thereactor containing a bed of fluidized powdered iron catalyst. Conditionsfor a typical run will be given hereinafter, together with the yield. Asstated, carbonaceous deposits form on the catalyst and in, say, 100hours, as much as 50 pounds of carbon may be on each 100 pounds ofcatalyst. This will tend to destroy the activity of the catalyst andalso cause its physical disintegration so that fines in copiousquantities will appear in pipe 3 with the gasiform products instead ofremaining in the reactor as a dense suspension between the bottom of thereactor and the level L which I have chosen to represent the upper densephase level of the fluidized catalyst bed.

To correct this defect, I withdraw catalyst intermittently orcontinuously through a draw-oil pipe 4, and since the catalyst is hot(575 F. to 675 F.) I first quench it in water, contained in a receiver6, to about atmospheric temperature. The quenched catalyst is withdrawnfrom the vessel '5 by a conveyor 8, discharged on a drain or reticulatedconveyor I where water is permitted to drain oil", to the extent thatthe remaining water is about 2| weight per cent of the catalyst, thencedischarged into a mixer I? where a fuel (if necessary) may be added,such as oil, coal, coke, etc., and thence the iron or the iron-fuelmixture is fed into a grate bar conveyor. This grate bar conveyorcarries a moving screen, or

. other foraminous member, havin openings, say,

A, inch in size. In order to increase the porosity of the bed and tofurther regulate the fuel content of the mixture, if such regulation isdesirable, coars iron oxide from a supply hopper I5 is added to themixture. This coarse material may be previously used and resintered butunground catalyst, or it may be fresh, unused iron oxide. The amount ofthe coarse material added to the catalyst to be resintered may vary fromto 60% depending on the operating conditions desired in the resinteringoperation. A

layer of this mixture, say, 6 inches thick is fed on to the movingconveyor screen. The mass is then ignited (as by a torch) and the waxand/or carbonaceous material on the iron burns, aided by air suckedthrough the bed by applying a vacuum at the underside of said screen.Resintering or incipient fusion of the powdered catalyst occurs, thetemperature risin to about 2200" F. or higher. The resintering of theiron powder causes it to agglomerate to form particles of greater size,while at the same time, of course, the catalyst contaminants areconverted to gaseous material or fumes which are emitted from the iron.A productis obtained in hopper 20 from the grate it which can bere-ground to the desired size and recharged to reactor 5.

A test run was made of an iron catalyst which had become contaminatedwith carbonaceous deposits and wax, which product was resintered and itwas found that the resintered catalyst had good activity. The conditionsand yield appear below:

Run #34 Hours 92-115 Ratio of CO to H2 in feed gas c 1.14 Temperature,F. 600 Pressure, p. s. i. g 300 V/V/Hour 1 198 cc. 04+ per cubic meterHz-FCO consumed 198 contraction 61 V/V/Hr.=volumes of feed per volume ofcatalyst per hour.

A yield of around 200 cc. of liquid C4+ product per cubic meter of feedgas (CO+H2, measured at 60 F. and 1 atmosphere) is considered good.

Modifications of my invention will suggest themselves to those familiarwith the art. Obviously, the resintering may be accomplished in aretort, a tube, a chamber, etc. I have shown a practical method foraccomplishing the desired results continuously. Various wetting agentsmay be added to the quench Water in the quenching zone and also thepromoters may be added at this point. Also, alcohol or other liquid maybe used in the quenching medium! Furthermore, make up iron or iron oxidemay be added to the used catalyst fines prior to the sintering operationto replace catalyst unavoidably lost from the system. It will beobvious, of course, that the coarse iron fed onto the grate I3 must belarger in size than the openings in the screen I4 to form a layer whichwill prevent the fines in an upper layer from passing through theopenings in screen it.

Furthermore, since, of course, iron oxide is discharged into hopper 20,it is preferable to reduce this oxide to metallic iron in the presenceof hydrogen at a temperature of 700 to 900 F. before returning it to thereactor i.

What I claim is:

1. The method of synthesizing hydrocarbons and oxygenated hydrocarbonswhich comprises forcing a mixture. of gases containing carbon monoxideand hydrogen into a reaction zone containing a well-fluidized bed ofpowdered iron catalyst, maintaining hydrocarbon synthesizing conditionsof temperatures and pressures in the reaction zone, permitting thereactants to remain resident in the reaction zone for a suflicientperiod of time to effect the desired conversion, withdrawing iron fromthe reaction zone, quenching the same, heating the said powdered iron toa temperature of at least incipient fusion in the presence of anoxidizing gas whereby agglomeration pf the catalyst particles occurs,grinding the said particles to a size greater than the said powderediron removed. from the reaction zone and returning the ground iron tosaid reaction zone.

2. The method set forth in claim 1 in which the iron following quenchingis dried to the extent that it contains about 21 weight per cent ofmoisture.

3. The method set forth in claim 1 in which additional fuel is added tothe quenched powdered iron prior to subjecting it to the heat treatment.

4. The method set forth in claim 1 in which prior to subjecting the ironto the heat treatment, promoters are added thereto.

5. The method of synthesizing hydrocarbons and oxygenated hydrocarbonswhich comprises forcing a mixture of gases containing carbon monoxideand hydrogen into a reaction zone containing a bed of powdered fluidizediron catalyst, maintaining elevated temperatures and pressures in thereaction zone, permitting the reactants to iron following quenching isdriedto the extent that it contains about 21 weight per cent ofmoisture.

'7. The methodset forth in claim 5 inwhich additional fuel is added tothe quenched-powdered iron prior to subjecting it to the heatjtreatment.

8. The method set forth in claim 5 in which prior to subjecting the ironto the heat treatment, promoters are added thereto.

9. In the method of synthesizing hydrocarbons and oxygenatedhydrocarbons in a reaction zone in the presence of a fluidized bed ofpowdered iron catalyst, the improvement which comprises maintaining theiron in a fiuidizable state by withdrawing powdered iron, sintering thesaid iron in the presence of an oxidizing gas whereby carbonaceousdeposits and wax are burned and removed and the particle fines areagglomerated. thereafter grinding the agglomerated materiai to form apowder having a size of from 4.0 to 200 microns and returning the sameto the reaction zone.

10. The method setvforth in claim 9 in which v powdered iron catalyst isremoved from the reaction zone at a rate responsive to the tendency ofcatalyst fines to pass out of the top of the reactor, sintered andreground and returned to the ream tion zone so as to maintain at alltimes a particle size of iron catalyst inthe reaction zone suci'i thatit does not contain particles smaller than 26 microns to a. degreegreater than 20 per cent of the total catalyst.

MARNELL A. SEGURA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,355,016 Stein, Jr Aug. iii-i42,383,636 Wurth Aug. 2%, 191-45 2,393,554 Orgozaly Jan. 2:2, 151 46

